Sub-sea working and drilling apparatus



Nov. 26, 1968 R. A. MccLlNTocK 3,412,564

SUEVSEA WORKING AND DRILLING APPARATUS Filed Feb. 21, 1967 2Sheets-Sheet 1 Crew @eng-22,;

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SUB-SEA WORKING AND DRILLING APPARATUS Filed Feb. 2l, 1967 2SheetS-Sheet 2 ted tates ABSTRACT 0F THE DISCLOSURE Apparatus .andmethod for stabilizing floating structures, specificallysemi-submersible structures by coupling them to a permanent submergedstructure constructed on the ocean floor at a desired location. Theapparatus as described comprises a platform supported by .a ffoatablehollow cylindrical chamber having ballast tanks attached thereto and astationary submerged base structure .aflixed to the ocean floor andextending upwardly therefrom to a predetermined depth below the oceansurface. To stabilize the platform, the cylinder is coupled to thesubmerged base structure. The apparatus is described as beingparticularly applicable for stabilizing drilling platforms for offshore-oil drilling operations.

Background of the invention Field of the invention-This inventionrelates to the stabilization of floating vessels and structures. Moreparticularly this invention relates to the stabilization of floatingplatforms by coupling them to a permanent submerged structure.

Description of the prior art-Exploration and exploitation of oil .andother mineral resources on and below the ocean floor depends upon thestability of floating vessels `and structures under a variety of waveand tide conditions to conduct operations. Many other operations at seaalso require a stable platform.

Although not limited thereto, the present invention is particularlyapplicable to offshore drilling operations for oil, and will accordinglybe described in connection with such operations. It will be seen,however, that the present invention is also applicable to thestabilization of other floating structures including, such as, floatingobservation platforms and dry docks.

lIn the present state of the art, drilling beneath a body of water canbe accomplished from floating vessels and from fixed platforms. Fixedplatforms are huilt and permanently supported upon the ocean floor bylegs which position the drilling platform above the wave action of thewater surface. Such platforms are, of course, severely limited by thedepth of water in which they can be utilized. Furthermore, theseplatforms are expensive to build and must permanently remain at theiroriginal location. Therefore, when there is no more use for the platformit must be abandoned. Drilling vessels in which the drilling operationis carried on from a floating vessel are well known in the art. Thesevessels offer many advantages over fixed platform; one advantage beingthat of mobility, since they can move to and from any location quickly.A primary disadvantage of such drilling vessels is the relativeinstability of the deck of the vessel, which deck having the drillingderrick and equipment positioned thereon constitutes the drillingplatform. That is, since the drilling vessel is freely floating, it issubject to surface wave action. The same disadvantageous conditionsoccur #with semisubmersible floating platforms which rely upon buoyancychambers positioned below the lwave act-ion to support a platform abovethe wave action. For many operations conducted from floating structuressuch as visual tracking platforms, radar platforms, missile trackingstations and the like, no rolling motion of the platform can betolerated.

atent C 3,412,564 Patented Nov. 26, 1968 In accordance with the presentinvention, .a drilling or working platform is provided which can beeasily towed from one location to a new location, and which when placedin position is completely stable. This is .accomplished by building abase structure below the wave action, which structure is permanentlyaffixed by legs to the ocean floor at la desired location. A platformhaving means for increasing or decreasing its buoyancy is positionedover the base structure. The buoyancy of the platform is then decreaseduntil it is partially submerged. It is then attached to, and supportedby, the base structure. Upon completion of the drilling or otheroperation, the platform is disconnected from the base structure, itsbuoyancy is increased and -it can be floated to a new location.

Accordingly, it is a primary object of the present invention to providea drilling and working structure 'which includes a floatable structurethat can be partially submerged such that itis connected to andstabilized by a submerged structure located at a predetermined loc-ationon the ocean floor.

Another object of the present invention is to provide a floatableplatform that can be stabilized by attachment to a base structurepermanently situated on the ocean floor.

Yet `another object of the present invention is to provide an apparatuswherein the base stmcture provides a submerged platform upon which wellhead equipment is mounted for drilling, completion, and productionsoperations.

Summary of the invention The present invention comprises in gener-alterms a base structure located on the ocean floor; a working platformhaving an upper surface and a lower surface oriented in a generallyhorizontal plane; and a floatable hollow Chalmber. The ilotable hollowchamber has a vertical axis, an upper end and .a lower end, and dependsvertically downward from the lower surface of the platform. The lowerend of the lloatable hollow chamber is selectively mateable with theupper surface of the base structure. The working platform is verticallyspaced .above the lower end of the floating structure by a sufficientdistance such that lwhen the floating structure is positioned upon thesubmerged base structure the Working platform is positioned above thewave and surface .action of the Water.

The novel features which are believed to be characteristic of theinvention, both as to its organization and method of operation, togetherwith further objects and advantages thereof will be better runderstoodfrom the following description considered in connection with theaccompanying drawing in which a presently preferred ernbodiment of theinvention is illustrated by way of example. lt is to be expresslyunderstood, however, that the drawings are for the purposes ofillustration and description only, and are not intended as a denition ofthe limits of the invention.

Brief description 0f the drawings `In the drawings:

FIGURE 1 is a view in elevation and partly in section of an illustrativeembodiment of the present invention;

FIGURES 2a through 2f are sequential partially schematic views of t-hevarious steps of assembly of the presently preferred embodiment of thepresent invention in which;

FIGURE 2a shows the floatable structure being towed in location;

FIGURE 2b shows the submerged base structure in location;

FIGURE 2c shows the floatable structure in position over the basestructure prior to partial submergence of the floatable structure;

FIGURE 2a' shows the floatable structure connected to the submergedstruct-ure with drilling operations being carried out;

FIGURE 2e shows the base structure with a pl-urality of wells drilledand completed; and

FIGURE 2f shows the base structure extended above the water surface as aproduction structure.

Referring now to FIGURE l a base structure 3G comprises legs 33, asubmerged platform 31 and vertically oriented mating members 34 and 34a.The base structure is constructed with the submerged platform 31supported by legs 33 which are sunk into the ocean floor l6G to a depthsuicient to obtain stability of the structure. The construction of thelegs is of the type well known to the art being of any suitablestructural configuration suc-h as those presently employed on drillingplatforms. The platform 31 can conveniently be located 40 to 160 ft.beneath the surface of the water so that lwhen chamber 2t) is submer-gedit can rest on platform 31 while platfor-m 1t) remains above the surfaceof the water. As will become more apparent hereinafter, the depth of thesubmerged platform is predetermined such that divers can convenientlyWork upon it while it is sufficiently below the water surface as to bebeneath wave and surface action of the water and constitute nonavigational hazard. For these reasons its depth will vary dependentupon the location and the characteristics of the body of water and thelength of the legs 33 will vary correspondingly and according to thedepth of the water. Typically, platform 31 is located 8() ft. beneaththe surface of the water. Base structure 30 can be constructed to aheight of up to S ft. above the ocean floor, the limits of such astructure being determined by structural and construction limitations.Typically, the height of the base structure is about 20() ft. fordrilling in water depth of approximately 250 to 30G ft. Platform 31 ofthe base structure has a plurality of conduits 36 passing u therethroughto allow pipe, drill strings or other equipment to pass through to theocean floor. Means for locating and laterally coupling the xiloatablestructure to the base structure are provided. In the presently preferredembodiment projecting vertically upward from surface 32 of platform 31are at least two male mating members 34 and 34a which are adapted toengage cavities 26 located on the underside of the base of chamber 20.Additional male mating members and 35a are also provided on uppersurface 32 of the submerged platform 31 for coupling and water sealingas described hereinafter.

The tloatable portion of the apparatus comprises a hull or housing 20and a working platform designated generally as 10. The housing 20 isoriented in a vertical position with the platform 10 supported at theupper end thereof in a generally horizontal plane. The working platform10 comprises a structure having all of the conventional drillingequipment and necessities at a remote drilling location such as livingquarters for a crew, a radio shack, a helicopter deck generators andother equipment. In the presently preferred embodiment of the inventionthe platform 1t) is typically 200 ft. long by 100 ft. wide and isspecifically adapted to support a derrick 12 and other equipment usedfor oil drilling operations including a rotary table 13 and mud pumps15. In the embodiment shown a riser string having a mud return linebelow the derrick floor is utilized. The riser is shown as 18 anddrilling is carried on through the riser in the conventional manner. Theriser is such that it can be deflected to be attached to any of aplurality of well heads positioned at the submerged platform 31 asdescribed hereinafter.

The hull or housing 20 is a hollow cylindrical body having a verticalaxis and which at its upper end is connected to the lower surface 16 ofplatform 10. The housing 20 thus defines a cylindrical working chamber22 extending from the working platform 10 to the submerged platform 31.The chamber 22 is closed at its upper end by the lowermost deck of theworking platform 10. Proximate the lower end of the chamber 22 is aworking deck 23 which is spaced from the upper surface 32 of thesubmerged platform 31. The lower end of the chamber 22 is thus open andsurrounded Iby the annular' ballast and storage chambers. The workingdeck has a plurality of guide openings 23a therethrough with waterclosures 27 which can be opened to deflect and guide the riser assembly18 to any of the desired well head locations 19 through the submergedplatform. Attached to the lower end of chamber 20 and integral with itaround its periphery are oatation tanks 24 by which means the buoyancyof housing 20 (with platform 10 attached) can be selectively increasedor decreased. Situated on the base of housing 20 are cavities 26 and26a, and 37 and 37a which are adapted to engage male mating members 34and 34a and sealing members 35 and 35a located on the platform 31 ofbase structure 30.

When the apparatus is assembled platform 10 is supported by 'housing 20which at its lower end is attached to base structure 30. Thus, theworking platform 10 is above any surface or wave action, and presents astable work platform for drilling or other operations. The chamber 22when the oatable structure is assembled on the base structure iswatertight and space 22 within the cylinder can be adapted as a workingchamber and for the storage of equipment. During drilling operationswell herad equipment is attached to the conduit 36 through whichdrilling operations are to be carried out. That is, the submergedplatform 31 is in effect the subsea well head location when theapparatus of the present invention is utilized. The well head equipmentusually comprises conventional blowout preventers, connect anddisconnect apparatus, and the like. The distance between the workingdeck 23 and the submerged platform 31 is sufficient to allowinstallation of such well head drilling equipment as well as completionand production equipment when a producing well is drilled.

A drill string 11 is passed through the turntable and riser 18downwardly through conventional well head drilling equipment 29 andthrough conduit 36 located in platform 31 into casing 36a which extendsinto the well bore. Seals such as 35 and 35:1 surrounding the open endof the chamber 22 prevent the entry of appreciable quantities of waterinto chamber 22, therefore all equip- .ment located within the cylinderis easily accessible without the need for diving equipment. Any waterthat does enter the chamber 22 can be easily pumped from the chamber. Anaccess 2f with suitable closure is provided through the working deck tothe well head at the platform 30.

The flotation means comprises a hollow annular body 24 attachedproximate the lower end of cylinder 20 and circumventing the peripherythereof. The hollow body 24 can be divided into several compartmentscomprising ballast tanks and fuel tanks. It is the function of annularbody 24 to increase or to decrease the buoyancy of the structure, and tomaintain cylinder 20 in an upright position when it is floating andunattached to base structure 30. On the underside of annular body 24 area series of indentations 26 and 26a and 37 and 37a. These indentationshave dimensions sufficient to accommodate mating ymembers 34 and 34a and35 and 35a protruding upwardly from surface 32. These dimensions aresuch that chamber 20 when in position on platform 31 is restrained frommoving in any lateral direction in response to wave action. Theseindentations are so positioned that when cylinder 2@ is lowered ontoplatform 31, they will be engaged by mating members 34 and 34a and 35and 35a and cylinder 20 is thereby coupled to base structure 30. Whenindentations 26 and 26a and 37 and 37a are engaged by mating members 34and 34a and 35 and 35a a water tight seal is established between thebase of annular body 24 and surface 32 of platform 31. Typically, thelength of the housing 20 is 120 feet. When the housing is coupled to thebase structure 30 the platform 10 is supported 40' feet above thesurface of the water and feet of the cylinder are submerged beneath thesurface of the water.

With reference to FIGURES 2a-2f there are shown steps in the method ofstabilizing the `drilling and working structure at a desired location.yIn FIGURE 2a is shown the floatable structure in a semi-submersiblecondition as it is being towed to a desired location. Specifically, thedrilling platform integral with the housing or hull is towed to adesired location; the buoyancy of the structure is provided by thehollow annular body 24 which comprises ballast tanks and storage tanks.Exploratory wells can be drilled to determine the limits of the oilfield. When the most advantageous location has been determined, thesubmerged base structure 30 is constructed at the desired location, asshown in IFIGURE 2b. The base structure comprises the submerged platform31 and legs 33 'which are embedded in the ocean floor 60 to a suitabledepth sufficient to insure stability of the entire structure. After thefloatable structure has been towed to the location above the submergedstructure, ballast tanks located in annular hollo-w body 24 are filledwith water or any other `desired ballast to decrease the buoyancy of thefloating structure. As the buoyancy decreases, the iloatable structureis partially submerged luntil annular body 24 rests upon surface 32 oft-he submerged base structure as shown in FIGURES 2c and 2d. Coupling ofannular body 24 to platform 31 is accomplished when indentations 26 onthe underside of body 24 are engaged by vertical mating members 34 and34a and 35 and 35a which protrude vertically from surface 32 of platform31. With cylinder 20 ballasted down and coupled to platform 31, drillingplatform 10 is above the `wa-ve action, and offers a very stable workingsurface for driling or other operations. Upon completion of drilling,the wells 36 are completed at the depth of platform 31 which is a depthaccessible to divers. The floatable platform is removed from the basestructure by removing ballast from the ballast tanks and thereby causingthe structure to rise in the water, thus disengaging the mating membersand causing platform 31 to float. The annular body 24 serves as afloating base for cylinder 20 and for platform 10 which is supportedabove the surface of the water by the cylinder. In this position theplatform can be towed to a new location. After the floatable structureis towed away, the submerged platform serves as a series of well headbases below the wat-er surface as shown in `FIGURE 2e. At this depth theplatform is easily accessible to divers. if the wells are productionwells, production equipment can be installed at this depth or, as shownin FIGURE 2f an extension can be placed upon the submerged platform toraise the well heads above the surface Where production or completionequipment indicated generally as 36 can be most conveniently installed.

It is apparent from the foregoing that the invented apparatus and methodoffers many advantages over prior art apparatus and methods forstabilizing floating platforms and structures. The oatable platformwhich is the subject of the present invention is mobile and can be towedfrom one location to a new location. Furthermore, the present platformcan be used in deeper waters than prior art platforms which arepermanently supported by legs embedded in the ocean floor. When inposition at a drilling location, the present apparatus offers morestability than prior art floating vessels and the like. Anotheradvantage of the present invention is that unlike prior art fixeddrilling platforms that are abandoned at the site the drilling platformof this invention can be reused numerous times at new locations, it istherefore far more economical than prior art platforms. Still anotheradvantage of the apparatus employed in this invention is that the workarea in which the drill string is connected to riser pipes at thesurface of the submerged platform is in a protected water freeenvironment and `is easily accessible `for repair or maintenance withoutthe need for divers when the oatable portion is in position, and is at adepth Iwhere divers can work comfortable when the floatable structure isnot in position.

Although this invention has been disclosed and illustrated withreference to particular applications, the principles involved aresusceptible of numerous other applications which will be apparent topersons skilled in the art. The invention is, therefore, to be limitedonly as indicated by the scope of the appended claims.

What is claimed is:

1. A sub-sea drilling and working apparatus cornprising:

a base structure including legs affixed to and extending upwardly fromthe sub-sea floor, a submerged platform at the upper end of said basestructure, said submerged platform being spaced a substantial distancefrom said sub-sea oor by said legs and at a submerged depth below thewave land surface action of the water,

a oatable hull removably coupled to said base structure, said hullincluding a hollow housing having a vertical axis with means forcoupling the lower end thereof to said submerged platform, a workingplatform axed at the upper end of said hull transverse to the verticalcenterline of said hull, said working platform being spaced abofve thewave and surface action of the water by the height of said hollowhousing,

said housing defining a working chamber within said Ihollow housingbetween said yworking platform and said submerged platform, means forexcluding water from said working chamber,

means for selectively increasing or decreasing the buoyancy of said hullto couple and decouple said hull to said base structure; and

drilling equipment positioned on said working platform, well headequipment positioned on said submerged platform.

2. The apparatus as defined in claim 1 in which said drilling equipmentincludes a derrick and rotary table on said working platform, said wellhead equipment includes a blowout preventer at said submerged platformand a well conduit extending from said submerged platfor-m into a wellbore in the sub-sea floor.

References Cited UNITED STATES PATENTS 2,217,879 10/1940 Willey (S1-46.5X 2,736,172 2/1956 McChesney 61-46 2,912,828 11/1959 Gerwick 61--522,940,266 6/ 1960 Smith 61-465 3,036,438 5/1962 Sims 61-46.5 X 3,138,9326/1964 Kofahl et al 61-465 3,307,624 3/ 1967 Lubinski 61-46.5 X

JACOB SHAPIRO, Primary Examiner.

